Plastic fasteners enjoy widespread use in the automotive industries and in other industries in applications where an object must be secured to a relatively thin substrate such as the sheet metal frame or body of an automobile. An ideal plastic fastener can be inserted into a bore formed through a substrate relatively easy but is difficult to withdraw.
Unfortunately, one characteristic of plastic fasteners of this type is that because the fasteners themselves are fashioned of relatively flexible materials, fasteners that are easy to insert into a bore formed through a substrate tend to be relatively easy to remove from the substrate. Similarly, where a fastener is difficult to remove from a substrate, it is generally correspondingly difficult to insert that fastener into the bore formed through the substrate. Accordingly, there is a need for a reusable plastic fastener that may be easily inserted into a bore formed through a substrate, yet is difficult to remove from the substrate. In addition, it is desirable to provide a fastener that may be reused so that fasteners need not be replaced each time they are disassembled. This former need is particularly useful considering that in the manufacture of an object such as an automobile, a component being attached to an automobile frame or body may need to be removed temporarily for repair or adjustment.
U.S. Pat. No. 6,305,055 to Castro, hereby incorporated by reference, is intended to meet the aforementioned needs by providing a plastic fastener having a shaft with two curved, flexible flanges secured thereto that flex inwardly as the shaft of the fastener is forced into a bore formed through a substrate. The flanges resist withdrawal once the fastener had been fully inserted into the bore. While the fastener described in the '055 patent performs admirably, the ratio of the force required to insert the fastener into a bore to the force required to withdraw the fastener from the bore is not ideal. Accordingly, the present invention provides a fastener having an improved insertion to withdrawal force ratio and which is constructed so as to be easily reused after disassembly.